The plan is to leave the Nissan BMS exactly where it is, and just replace the cells. The Leaf BMS wiring loom is great because it's modular with HV wiring loomed back to a central unit. It should be far easier to swap the cells from underneath than the iMiEV where they are integrated into the tops of the cell blocks.

I should add I'm happy to do this from Perth - I know Damien Butcher in Canberra was doing something similar over east.

But are you going to get the same voltage verses capacity curve from the different cells? And if not can the software be hacked and a new "curve" written in ?

quote=brunohill post_id=69112 time=1534504534 user_id=4860]
This guy probably answers your question Terry...www.youtube.com/watch?v=k3jaGtkyxvA
[/quote]
This video you posted and the following up ones he has about range bring up the very real issue of discharge curves. His results are basically the guess o meter is no longer accurate so that may be a downside that people will have to live with when doing battery mods.

Also thanks for posting that, I was up half the night watching some guy from Europe faff about on his leaf tek screwing covers to his rims for better aerodynamics and other random hacks.

It is not only the guessometer that will be out, but the car may actually stop with 50% capacity left. You could make a resistor voltage divider arrangement off each cell (between it and the total pack) to trick the system into thinking the voltage is higher than it is and still monitor balancing, when the voltage is low. But... This would have to be switched out when charging and when the battery is at a high state of charge. Big job, messy, and would need to be reliable. A software solution would be easier, if you knew how?

Last edited by brunohill on Sat, 18 Aug 2018, 20:45, edited 1 time in total.

The only one I saw working properly had two separate packs. The original as is, and a second one external and connected after the battery ecu current sensor. The car just saw the original battery discharging slower.

In terms of the extender battery, I wonder how the car would react if you disabled the factory battery and ran purely off the 2nd batt. It would see no discharge and It would probably throw an error code but would it still drive OK? If so leave the main pack, add a 2nd and just have a change over switch, rather than running the 2 batteries in parallel. Start off on the aux/2nd batt until it's discharged then switch back to the factory to continue driving.
That way the cars main battery pack would still be full while on the 2nd batt and low charge/turtle mode would not come up.
You'd have to charge them separately as well because they'd be way out of sync.

I agree that a software hack and upgrade the main cells would be the way to go but I feel that a nissan software engineer purposefully went out of his/her way to make it near impossible.
So add your own bms etc for the new cells and fit 1 x 18650 per cell on the main pack that won't discharge for the factory bms to read and be happy with. Or more elegantly just supply 3.5v to each sense wire on the oem bms

It is not only the guessometer that will be out, but the car may actually stop with 50% capacity left. You could make a resistor voltage divider arrangement off each cell (between it and the total pack) to trick the system into thinking the voltage is higher than it is and still monitor balancing, when the voltage is low. But... This would have to be switched out when charging and when the battery is at a high state of charge. Big job, messy, and would need to be reliable. A software solution would be easier, if you new how?

According to the Kiwi guys who pulled a 30 kWh Leaf battery apart, the product code on the BMS is exactly the same as the 24 kWh pack. So if it needs any tweaking, it would be the BMS software. Hopefully it can start to learn the new discharge profile after a full re-start.

According to the Kiwi guys who pulled a 30 kWh Leaf battery apart, the product code on the BMS is exactly the same as the 24 kWh pack. So if it needs any tweaking, it would be the BMS software. Hopefully it can start to learn the new discharge profile after a full re-start.

Is it situation that Nissan onboard computers are more straightforward than VIN-locked Mitsubishi versions ? A while back, enginer was claiming it could add a second battery pack to a 24kwh Leaf although to the best of my knowledge that didn't work like the publicity blurb suggested. talking about non-factory battery packs is all very well, but to date I'm not aware of anyone actually making this work.

There is no VIN locking on the battery cells, just the BMS in the battery pack allegedly. If cell voltage curves are similar it does not know the difference. A petrol car does not know if the fuel came from Shell or BP but you may have some trouble making it work if you use a non genuine fuel pump.

Using the "claimed" 3.6V 42Ah is a 30% increase over the standard leaf module.
Is it worth the effort?

It could be when the original pack reaches the end of useful life in the vehicle. It maybe cheaper too.
The 100 Ah units will fit in the leaf battery pack (with room to spare) but a major redesign of the wiring loom and mounting modifications would be required. Modules of 4 batteries in series may be the way to go. The result should be a 36 kW to 39 kW LEAF ( cheaper than a new LEAF).

The 42Ah 2S2P are about the same size as the LEAF modules. There is not enough room to do this with the 100 Ah batteries but 96 of them will fit in the battery pack. The 135 Ah won't fit in the battery housing.

https://www.youtube.com/watch?v=d-ka4-mG_0I
In this video the guy explains how retaining the vehicle's original BMS was the easiest way to keep the vehicle's onboard computer happy.
So I might try and re-pack a Leaf battery with a new BMS and wiring, but have it so you can swap the BMS at the last minute.